MONTE-CARLO SIMULATIONS ON THE COERCIVE BEHAVIOR OF OXIDE-COATED FERROMAGNETIC PARTICLES

The Monte Carlo simulation technique has been used to study the coerci vity of small ferromagnetic particles covered by an antiferromagnetic shell. In particular, we examine its size and temperature dependence. We find that the exchange interaction between the ferromagnetic core a nd the antiferromagnetic shell of the particles causes a reversal in t he size dependence of the coercivity at low temperatures. The enhanced interface anisotropy results in a considerable increase of the coerci vity, and in a more rapid fall with temperature. Our simulations sugge st that the steep temperature dependence of the coercivity observed in experiments, should be attributed to the strong temperature dependenc e of the anisotropy of the antiferromagnetic shell.